Thermoplastic polymer fibers, particularly nylon and polyester fibers, have been widely used for many decades due to their high strength and wear characteristics. Such fibers in high denier ranges, particularly those greater than about 30 denier, have been used in industrial applications such as the manufacture of dish scouring pads and buffer pads. Thermoplastic polymer filaments are commonly manufactured by extruding liquified polymer through the holes of a round, solid spinnerette, then cooling the liquified polymer in a flow of air or inert gas to form solidified filaments. The filaments can also be drawn to further orient the polymer and produce the desired final size of filament.
Because the production of larger diameter fibers requires the solidification of a greater amount of polymer, it has previously been difficult to cool large denier filaments in a rapid manner using such an air or gas flow. In particular, an air flow is often insufficient to cool such larger filaments quickly enough to avoid their sticking together before they solidify. Alternatively, applying a greater amount of air can damage the filaments because the air speed required is often stronger than the filaments can withstand.
As a result, large denier filaments are conventionally spun into a water quench bath in order to solidify the polymer filaments. Water quenching of the filaments tends to greatly limit the process speed, however, because high process speeds tend to generate turbulence in the quench bath which in turn damages the filaments.
Therefore, the need exists for a method of making higher denier thermoplastic polymer filaments at more rapid throughput speeds.